The pen of the poet (5)
I believe the answer is:
pound
I believe this clue is a double definition.
'the pen' is the first definition.
(both can mean an animal enclosure)
'the poet' is the second definition.
(I've seen this in other clues)
'of' is the link.
(Other definitions for pound that I've seen before include "100 6 [PENNIES]" , "British currency" , "Batter" , "Weight - currency - beat - enclosure" , "PS" .)